What was encaustic
"Despite investigations, during the last fifty years and more, by numerous and able scholars, the essential problem of the encaustic technique, particularly as revealed in the Fayum portraits, remains unsolved. What kind of wax formed the binding medium for the pigments? Was any other substance added to the wax? No single authority has given us a set of recorded objective data which alone would furnish an answer to these questions". Elizabeth Dow. The medium of encaustic painting. Technical studies in the field of the fine arts 5 (1936), 2.
"Since the Renaissance, no other painting technique has been subject to such zealous and detailed attempts to explain its methods, materials, and utensils as the encaustic technique of antiquity". Kurt Wehlte. Werkstoffe und Techniken der Malerei. 1967, 8.8.
"Opinions vary as to the nature of the binding medium used for the execution of the mummy paintings. Petrie, for example, suggests that unmodified beeswax was simply purified by heat prior to the addition of powder pigments. Berger, on the other hand, referring back to Pliny's account of the encaustic painting technique, claims that Punic wax acted as the binding medium. [...] As Punic wax was interpreted to be an emulsion composed of alkali-treated beeswax, Berger indicates that the binding medium could have been manipulated with a brush. Other suggestions concerned with a possible method of preparing the binding medium have involved the addition of a resin of a maritime pine to beeswax, or the admixture of Chios balsam and olive oil to Punic wax". Brian Ramer. The technology, examination and conservation of the Fayum portraits in the Petrie Museum. Studies in conservation, 24 (1979), 3.
"The technique of ancient encaustic, in which most of of the Fayum portraits were painted, remains something of a mistery. From the eighteenth century onwards a number of artists and scholars have tried to uncover its secrets, an effort that accelerated with the finds of larger numbers of such portraits at the end of the nineteenth and beginning of the twentieth century and continues to occupy researchers from various disciplines to this day". Euphrosyne Doxiadis. Technique. Ancient Faces. Mummy Portraits from Roman Egypt. 1997, 21.
"Literary references in antiquity to the origin and development of the encaustic technique are scarce and often obscure. The vast number of interpretations regarding these ancient treatises fail to reach a distinct conclusion". Athina Alexopoulou-Agoranou, Alexandra-Eleni Kalliga, Urania Kanakari, Vassilios Pashalis. Pigment Analysis and documentation of two funerary Portraits Which Belong to the collection of the Benaki Museum. Portraits and Masks, 1997, 91.
"It is possible that encaustic painting is, among all the painting techniques, that which has aroused most controversy among theorists and artists themselves, to the point of having generated at times a real bibliographic "war". Free interpretation, bewilderment, but also continual research, have surrounded always a way of painting associated with the legendary mastery of Apelles, the artist known in antiquity by his encaustic works. [...] When trying to collect materials and methods on the encaustic we only get to follow the line in a long and controversial investigation. The discussions on the medium itself of this technique, ie wax, were and are endless". Cristina Morilla. La encáustica. Descubrir el arte 16 (2000) 104-105.